Utilizing clock shield as defect monitor
a clock shield and defect monitor technology, applied in short-circuit testing, instruments, measurement devices, etc., can solve problems such as initial test failur
Inactive Publication Date: 2006-03-30
INT BUSINESS MASCH CORP
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Benefits of technology
[0009] The invention first performs initial testing of the shielded clock tree. If the shielded clock tree fails the initial testing, the invention activates the switches that are connected to the shielding that is adjacent to the clock signal wiring to disconnect the shielding from ground, and then retests the shielded clock tree. If the shielded clock tree passes this retesting process, this indicates that the initial test failure was probably caused by one of the clock signal wires shorting to ground through one of the shields. Therefore, if the shielded clock tree passes the retesting process, in order to determine the location of the defect, the invention selectively activates the switches to selectively disconnect portions of the shielding from ground (e.g., disconnecting one or more shield wire at a time), and then repeatedly tests the shielded clock tree with different switches activated to locate one or more defects. During this process of disconnecting individual (or groups of) shield wires from ground, if the shielded clock tree passes the retesting process, this indicates that a short between a clock signal wire and the shield wire(s) that was disconnected may be one of the sources of the defect(s) that caused the shielded clock tree to fail the initial testing. This allows the invention to know precisely which shield wire (or group of shield wires) has potentially caused the defect. This, in turn, allows the circuit design, circuit layout, or manufacturing process to be analyzed and corrected.
Problems solved by technology
If the shielded clock tree passes this retesting process, this indicates that the initial test failure was probably caused by one of the clock signal wires shorting to ground through one of the shields.
Method used
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[0017] The present invention and the various features and advantageous details thereof are explained more fully with reference to the nonlimiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the present invention. The examples used herein are intended merely to facilitate an understanding of ways in which the invention may be practiced and to further enable those of skill in the art to practice the invention. Accordingly, the examples should not be construed as limiting the scope of the invention.
[0018] In this invention the hardwired bias to the shields is replaced with a circuit which can optionally tie the shields to ground or let them float based on a test control signal. In the tied-down state, the shields pro...
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Disclosed is a shielded clock tree that has one or more clock signal buffers and clock signal splitters, with clock signal wiring connecting the clock signal buffers to the clock signal splitters. Shielding is adjacent the clock signal wiring, where ground wiring connects the shielding to ground. The shielding comprises shield wires positioned adjacent and parallel to the clock signal wiring. The invention provides switches in the ground wiring, and these switches are connected to, and controlled by, a test controller.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a division of U.S. application Ser. No. 10 / 710,222, filed on Jun. 28, 2004.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention generally related to shielded clock trees and more particularly to a shielded clock tree that includes switches in the ground wiring that connects the shields to ground, where the switches are adapted to connect the shielding to ground during non-test operations and to selectively disconnect the shielding from ground during test operations. [0004] 2. Description of the Related Art [0005] Clock shielding is used to electrically isolate major portions of a clock tree within an integrated circuit structure. In general, the shielding is used on all portions of the clock tree up to the clock splitters. The shielding is generally implemented as grounded, minimum size, and minimum spaced wires on either side of the clock running segment, as shown in FIG. 1. More...
Claims
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IPC IPC(8): G01R31/26G01R31/02G01R31/30G01R31/317
CPCG01R31/025G01R31/31727G01R31/31725G01R31/30G01R31/52
InventorCOHN, JOHN M.PASTEL, LEAH M.P.SOPCHAK, THOMAS G.VALLETT, DAVID P.
OwnerINT BUSINESS MASCH CORP